Co-production as a mechanism for long-term Nature-based Solution viability: evidence from urban biofilters in an informal settlement of the Global South

Barbara Marion Gomez , Camila Saveika, Rodrigo Sinistro, Martin Graziano

Assessing the long-term viability of Nature-based Solutions (NbS) in vulnerable urban contexts remains a major methodological challenge. Existing assessment frameworks primarily emphasize technical performance while giving limited attention to physical device survival and the continuity of the socio-technical arrangements required to sustain interventions over time. This study develops and empirically evaluates an integrated assessment framework in which these three dimensions are understood as interdependent components linked through feedback mechanisms. The framework was tested through a four-year longitudinal study (2019–2023) of a co-produced NbS intervention in the San Francisco stream (Claypole, Buenos Aires, Argentina), where 15 modular intermittent vertical-flow biofilters were implemented through a transdisciplinary partnership between academic institutions and a local social organization. Results showed that long-term NbS viability emerged from the interaction among the three dimensions rather than from any single component in isolation. Biofilters consistently removed organic matter (COD and DOC), with performance varying seasonally and reaching maximum removal during spring (47.2 ± 18.2% and 49.3 ± 13.7%, respectively; mean ± SD), whereas net dissolved nitrogen removal remained limited (1.2 ± 40.6%). Device survival was determined by local hydraulic exposure (watershed side; p = 0.009), rather than cumulative rainfall, highlighting the importance of site selection for both implementation andperformance evaluation. The continuity of the socio-technical arrangement sustained monitoring and maintenance throughout the COVID-19 restrictions, suggesting that system resilience depended as much on socio-technical organization as on hydraulic design. Together, these findings indicate that evaluating NbS in vulnerable urban contexts requires integrating technical performance, physical device survival, and socio-technical continuity within a single assessment framework. Co-production emerged not simply as a participatory strategy but as the mechanism coupling these dimensions, with direct implications for the design, evaluation, and scaling of NbS in urban peripheries of the Global South.